auto import from //depot/cupcake/@135843
diff --git a/libc/string/memmove.c b/libc/string/memmove.c
new file mode 100644
index 0000000..fcaf4ee
--- /dev/null
+++ b/libc/string/memmove.c
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <string.h>
+
+void *memmove(void *dst, const void *src, size_t n)
+{
+ const char *p = src;
+ char *q = dst;
+ if (__builtin_expect(q < p, 1)) {
+ return memcpy(dst, src, n);
+ } else {
+#define PRELOAD_DISTANCE 64
+ /* a semi-optimized memmove(). we're preloading the src and dst buffers
+ * as we go */
+ size_t c0, c1, i;
+ p += n;
+ q += n;
+ /* note: we preload the destination as well, because the 1-byte at a time
+ * copy below doesn't take advantage of the write-buffer, we need
+ * to use the cache instead as a poor man's write-combiner */
+ __builtin_prefetch(p-1);
+ __builtin_prefetch(q-1);
+ if (PRELOAD_DISTANCE > 32) {
+ __builtin_prefetch(p-(32+1));
+ __builtin_prefetch(q-(32+1));
+ }
+ /* do the prefetech as soon as possible, prevent the compiler to
+ * reorder the instructions above the prefetch */
+ asm volatile("":::"memory");
+ c0 = n & 0x1F; /* cache-line is 32 bytes */
+ c1 = n >> 5;
+ while ( c1-- ) {
+ /* ARMv6 can have up to 3 memory access outstanding */
+ __builtin_prefetch(p - (PRELOAD_DISTANCE+1));
+ __builtin_prefetch(q - (PRELOAD_DISTANCE+1));
+ asm volatile("":::"memory");
+ for (i=0 ; i<32 ; i++) {
+ *--q = *--p;
+ }
+ }
+ while ( c0-- ) {
+ *--q = *--p;
+ }
+ }
+
+ return dst;
+}